Anyone is more than welcome to implement a similar window/app switching mechanism in their favorite environment on whatever distro they wish. It is not up to UBports to implement window switching enhancements in other environment on other distros.

Unity8 is open source, and anyone can package it for their favorite distro and help do the work to make it usable. There's already work done on bringing it to Debian, Arch, Fedora, and SUSE, and that presumably means any derivatives thereof as well. However, the core UBports developers are not responsible for packaging it on other distros and integrating with them. There's also too much work to still be done with keeping the phones working and fixing issues there, to really concentrate on making Unity8 usable as a daily on PCs. There are also lots of changes on more recent distro releases which significantly impact Unity8/Mir usability, as described in the other thread started about Unity8 in 2019.